[RFC,3/4] resolv: fix issues when using IPv6 nameservers only
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Message ID 1401838603-22101-4-git-send-email-aurelien@aurel32.net
State New
Headers show

Commit Message

Aurelien Jarno June 3, 2014, 11:36 p.m. UTC
statp->nscount contains the number of servers in the statp->nsaddr_list
array, which only contains IPv4 nameservers.

When resolv.conf only contains IPv6 nameservers, statp->nscount equals
to 0, which causes the existing code to add a 127.0.0.1 entry. Change
that by checking nservall, contains the number of IPv4 + IPv6 servers
instead.

The same way __libc_res_nsend exits almost immediately when
statp->nscount considering that no nameservers are available, while
IPv6 nameservers are actually available. Change that by checking
(statp->nscount + EXT(statp).nscount6) instead.
---
 resolv/res_init.c | 2 +-
 resolv/res_send.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

Comments

Andreas Schwab June 4, 2014, 10:44 a.m. UTC | #1
There is another use of statp->nscount in send_dg.  That should be
changed as well, otherwise it can result in a div by 0.

Andreas.
Aurelien Jarno June 4, 2014, 7:20 p.m. UTC | #2
On Wed, Jun 04, 2014 at 12:44:13PM +0200, Andreas Schwab wrote:
> There is another use of statp->nscount in send_dg.  That should be
> changed as well, otherwise it can result in a div by 0.

Good catch, I fixed that locally, it will be in the next version of the
patches.

Patch
diff mbox

diff --git a/resolv/res_init.c b/resolv/res_init.c
index 37004ab..95564af 100644
--- a/resolv/res_init.c
+++ b/resolv/res_init.c
@@ -427,7 +427,7 @@  __res_vinit(res_state statp, int preinit) {
 #endif
 	    (void) fclose(fp);
 	}
-	if (__builtin_expect(statp->nscount == 0, 0)) {
+	if (__builtin_expect(nservall == 0, 0)) {
 	    statp->nsaddr.sin_addr = inet_makeaddr(IN_LOOPBACKNET, 1);
 	    statp->nsaddr.sin_family = AF_INET;
 	    statp->nsaddr.sin_port = htons(NAMESERVER_PORT);
diff --git a/resolv/res_send.c b/resolv/res_send.c
index af42b8a..08fc037 100644
--- a/resolv/res_send.c
+++ b/resolv/res_send.c
@@ -347,7 +347,7 @@  __libc_res_nsend(res_state statp, const u_char *buf, int buflen,
 {
   int gotsomewhere, terrno, try, v_circuit, resplen, ns, n;
 
-	if (statp->nscount == 0) {
+	if ((statp->nscount + EXT(statp).nscount6) == 0) {
 		__set_errno (ESRCH);
 		return (-1);
 	}